i965/vs: Restructure emit() functions around a vec4_instruction constructor.

We sometimes want to put an instruction somewhere besides the end of
the instruction stream, and we also want per-opcode instruction
generation to enable compile-time checking of operands.

src/mesa/drivers/dri/i965/brw_vec4.h

@@ -239,6 +239,12 @@ public:
       return node;
    }
 
+   vec4_instruction(vec4_visitor *v, enum opcode opcode,
+		    dst_reg dst = dst_reg(),
+		    src_reg src0 = src_reg(),
+		    src_reg src1 = src_reg(),
+		    src_reg src2 = src_reg());
+
    struct brw_reg get_dst(void);
    struct brw_reg get_src(int i);
 
@@ -384,6 +390,8 @@ public:
    bool dead_code_eliminate();
    bool virtual_grf_interferes(int a, int b);
 
+   vec4_instruction *emit(vec4_instruction *inst);
+
    vec4_instruction *emit(enum opcode opcode);
 
    vec4_instruction *emit(enum opcode opcode, dst_reg dst, src_reg src0);

src/mesa/drivers/dri/i965/brw_vec4_visitor.cpp

@@ -72,43 +72,52 @@ dst_reg::dst_reg(src_reg reg)
    this->fixed_hw_reg = reg.fixed_hw_reg;
 }
 
-vec4_instruction *
-vec4_visitor::emit(enum opcode opcode, dst_reg dst,
-		   src_reg src0, src_reg src1, src_reg src2)
+vec4_instruction::vec4_instruction(vec4_visitor *v,
+				   enum opcode opcode, dst_reg dst,
+				   src_reg src0, src_reg src1, src_reg src2)
 {
-   vec4_instruction *inst = new(mem_ctx) vec4_instruction();
-
-   inst->opcode = opcode;
-   inst->dst = dst;
-   inst->src[0] = src0;
-   inst->src[1] = src1;
-   inst->src[2] = src2;
-   inst->ir = this->base_ir;
-   inst->annotation = this->current_annotation;
+   this->opcode = opcode;
+   this->dst = dst;
+   this->src[0] = src0;
+   this->src[1] = src1;
+   this->src[2] = src2;
+   this->ir = v->base_ir;
+   this->annotation = v->current_annotation;
+}
 
+vec4_instruction *
+vec4_visitor::emit(vec4_instruction *inst)
+{
    this->instructions.push_tail(inst);
 
    return inst;
 }
 
+vec4_instruction *
+vec4_visitor::emit(enum opcode opcode, dst_reg dst,
+		   src_reg src0, src_reg src1, src_reg src2)
+{
+   return emit(new(mem_ctx) vec4_instruction(this, opcode, dst,
+					     src0, src1, src2));
+}
+
 
 vec4_instruction *
 vec4_visitor::emit(enum opcode opcode, dst_reg dst, src_reg src0, src_reg src1)
 {
-   return emit(opcode, dst, src0, src1, src_reg());
+   return emit(new(mem_ctx) vec4_instruction(this, opcode, dst, src0, src1));
 }
 
 vec4_instruction *
 vec4_visitor::emit(enum opcode opcode, dst_reg dst, src_reg src0)
 {
-   assert(dst.writemask != 0);
-   return emit(opcode, dst, src0, src_reg(), src_reg());
+   return emit(new(mem_ctx) vec4_instruction(this, opcode, dst, src0));
 }
 
 vec4_instruction *
 vec4_visitor::emit(enum opcode opcode)
 {
-   return emit(opcode, dst_reg(), src_reg(), src_reg(), src_reg());
+   return emit(new(mem_ctx) vec4_instruction(this, opcode, dst_reg()));
 }
 
 void